Reversible galvanic battery.



No. 727,117. 2 3 i Patented May 5, 1903.

UNIT D STATES PATENT OFFICE.

THOMAS A. EDISON, OF LLEWELLYN PARK, NEWJERSEY, ASSIGNOR EDISON STORAGEBATTERY COMPANY, OF ORANGE,'NEW JERSEY, 'A CORPORATION OF NEW JERSEY.

REVERSIBLE GALVANlC BATTERY.

SPEOIFIGATION forming part of Letters Patent No. 727,117, dated May 5,1903. Application filed October 3. 1902- Serial No. 125.802. (No model.)

v To all whom it may concern.- In a broad sense the invention consistsin Be it known that I, THOMAS A. EDISON, a combining with the activematerial another citizen of the United States, residing'at Llewmaterial,which is less oxidizable and more ellyn Park, Orange, in the county ofEssex easily reduced to the metallic state than the p 5 and-State of NewJersey, have invented aceractive material and in such quantity as will'55' rain new and useful Improvement in Reversibe sufficient to cause alarge bulk of the parhle Galvanic Batteries, of which the followticlesof the active material to be in metallic ing: is a description. contactthroughout the entire mass.

My invention relates to reversible galvanic In carrying out my inventionin connection Io batteries of the type heretofore suggested by with theiron" electrode of an iron-nickel bat- 6o me in which an alkalineelectrolyte is used teryI proceedas follows: Funely-divided oxid withinsoluble active materials, the latter beof ironpis reduced to themetallic state by hying preferably mixed with foliated or flake drogengas at about 900 Fahrenheit in any graphite'or similar substance toincrease the suitable and approved retort for the purpose.

conductivity of the active material. The pre- After the iron has thusbeen reduced it is per- 65. 'i erred combination-which I employ includesmitted to cool to normal temperaturewhile oxid of nickel as theoxidizing or depolarizing still surrounded by the gas, atmospheric air:element and'metallic iron as the oxidizable .being excluded to preventspontaneous oxielement. dation. When the temperature of the iron As anillustration of my invention I shall has been sufficiently reduced,water is forced describe it in connection with the'iron elec into theretort to expel the hydrogen gas, trode of a reversible galvanic batteryemployor the simultaneous introduction of water ing an alkalineelectrolyte; but its applicaand withdrawal of the gas is efiected in anybility to other electrodes used with such soludesirable way. Theintroduction of water 2 5 ti'ons will of course be understood. into theretort, as explained, prevents 0xida-,

Broadly stated, my invention resides in the tion of the iron to itsoriginal condition of discovery that if an easily-reducible metaloxidation. While the reduced iron is wet, like copper, mercury, orsilver is added to the retortis opened and the wet or moist conthe ironorother active material in the maketents are removed, surplus waterbeing go up of an electrode for a reversible galvanic drained off. Inthis operation a slight heat- 0 used.

battery employing an alkaline electrolyte beting takes place due toatmospheric oxidater electrical contact between the particles of tion;but the proportion of iron so oxidized is the active material issecured, so that the inconsiderable or at least uno'bjectionable. weightof active material will bereduced more While the reduced iron is wet,moist, or

5 than the additional weight of the readily-redamp, it may be mixed.with graphite or 8 ducible metal, while at the same time the cell otherinert conducting material even when will sustain a higher voltagethrough'the 'enexposed to the air and moldedinto briquets tire period ofdischarge than would be -.the for use in the complete cell withoutanysericaseif'the readily-reducible metal were not ous oxidation takingplace. To the iron in v a moist condition I add suflicient ammoniated oMy objects, therefore, are, generally speakcopper to produce asa finalresult a mixture ing,toiinsurebetterelectricalcontactbetween composed ofsixty-six per cent. of ironand the particles forming the active materialof thirtythree per cent. of copper, although an electrode in reversiblegalvanic batteries these proportions maybe varied consider- '4?employing alkaline electrolytes, to reduce ably.- The addition ofammoniated copper.

weight per unit of energy, and to produce a to the reduced iron resultsin the copper becell-wherein a higher voltage may be sus-' ingimmediately reduced to the metallic state tained throughout the wholeperiod of disby the reducing action of the iron, a portion charge thanwith batteries of the type hereof whose particles becomes oxidized. Inthis so-tofore suggested. y A reaction ammonia is liberated as a gas. As101 a result of this treatment the exterior'of used.

each active iron particle will be coated with a porous envelop of coppermixed with iron oxid. This mixture may be immediately molded intobriquets and used in the bat-' tery; but preferably about twenty percent. of foliated or flake graphite is added thereto in order tosupplement the coherence of the mass, renderits manipulation more easy,and

also increase electrical conductivity. I find in practice that thecopper thus added serves to place nearly the whole of the active iron ingood contact throughout the entire electrode, while at the same time theincreased efficiency of the iron more than compensates for the addedweight of the copper, so that the entire cell is somewhat-lighter perunit of energy than if the copper is not used.- Ialso find that theaddition of copper asexplained enables the cell to sustain a highervoltage through the whole period of discharge than is the case if ironand-graphite are alone While the tendency of the copper is to dissolvein an alkaline solution when subjected to forced oxidation, I find thatwh en added to an excess of reduced iron, as explained, the copper isnot oxidized when the with a deoxidizable-or depolarizingmaterialbattery is discharging. During the charging-operation the actionon both the iron and copper is of a reducing instead of an oxidizingcharacter. Consequently it becomes possible to add copper to theoxidizable electrode on discharge of, an alkaline reversible galvanicbattery the difliculties which would be met if used on discharge.

While the process above indicated is that which I prefer to follow, itwill of course be understood that many other methods of coating theactive iron particles with copper can be usedand will readily suggestthemselves to chemists. Several of these alternative processes will bebriefly referred to. For example, the red oxid of iron made b ignitingferrous oxalate at a very low temperature may be intimately mixedwith'dry ammostir-red while the necessary niated'copper, the mixturebeing actively moisture is being -evaporated by heat. To this mixtureabout twenty per cent. of 'flake-graphite is effectively added,

and-the composition is then molded into briquets and after beingassembled is subjected to electrolytic reduction; but with this processlong-continued use of the current is vto reduce the iron to a commer-vcially active condition. Instead, therefore, of reducing the mixtureelectrolytically after being formed into briquets and assemjgled in thepockets of supporting-plates, asex 'plained,-it is more desirable tosubject the mixture of red iron oxid-and ammoniated copper to hothydrogen gas, so that the copper will be entirelyreduced to the metallicstate and the iron partially or wholly so. After this reduction the massmay be allowed to cool inan atmosphere of hydrogen and be toelectrolytic or hydrogen reduction.

electrode in which without encountering any of subsequently flooded withwater to prevent heat to drive off the volatile radical of the salt andbeing then subsequently subjected Even the copper hydrate can be mixedwith the red oxid of iron and the mixture subsequently reduced eitherelectrolytically or by hydrogen treatment; but

the method which I have first described is regarded as preferable, as itseems to give the best results in actual use.

Instead of copper any other readily-reducible material may be employed,such as mercury or silver. The latter material is ob- Viously not at thepresent time practically available on account of itsexpense, but mercurycan be effectively used under certain conditions. For instance, aboutfifteen per cent. of precipitated oxid of mercury. may be mixed withfinely-divided iron reduced by hydrogen, as explained, both being maintained in a damp or wet state, and to this mass about twenty percent. offlake graphite it will be understood that 7 iron, the mixture beingsubjected to sufiicient may be added. Such an electrode when used in analkaline solution possesses a marked increase in its dischargingcapacity over an iron and graphite are alone used. With such anelectrode on discharging the mercury, like the copper, remains in themetallic state and insures contact of the greater bulk '01: throughoutthe electrode.

I do not regard the use of an easily-reducible metal, like mercury orcopper, as practically available in connection with a nickel or otherdepolarizing pole of an alkaline storage battery to thereby insurecontact between the particles of active materials, for the reason thatin charging such an electrode is subjected to forced oxidation, and themercury or copper would therefore be also oxidized,

in whichcondition it would not increase the contact between the nickelparticles and would, moreover,

be somewhat soluble in the solution. For the nickel or depolarizing poleof the battery, therefore, I prefer to use the electrode heretoforesuggested by me, in which a mixture of nickel hydroxid and flakegraphite is used, the large quantity of graphite employed insuringsufiicient contactwith the nickel particles for all practical purposesand the graphite being entirely unaffected by forced oxidation duringthe charging opera tion. It is preferable in assembling the battery thatthe proportion of electrolyticallyactive iron employed should be inexcess of the oxidizing capacityof the nickel on dig;

charge in order that when the battery is coma pletely discharged a smallproportion of the electrolytically-active iron will remain unoxidized.In this way I amiable to prevent any the active iron particles ingthebattery oxidation of the added material with absolute certainty. Unlessthese proportions are observed care will have to be taken in dischargnotto carry the'discha'rging operation so far as to result in oxidation ofthe added material.

Having now described my invention, what I claim as new, and desire tosecure by Letters Patent, is as follows:

said electrode containing nnely-divided metallic iron or an. oxidthereof mixed with an inert conducting material, and an easily-reduciblemetal, as and for the purposes set i pr and an inert forth.

3. An electrode for a reversible galvanic battery employing an alkalineelectrolyte, said electrode containing finely-divided metallic iron oran oxid thereof mixed with a flake-like inert conducting material and aneasily-reducible metal, as and for the'purposes set forth.

4. An electrode for a Zreversible galvanic battery employing an alkalineelectrolyte, said electrode containing finely-divided metallic iron oran oxid thereof mixed with flake graphite and an easily-reducible metal,as and for the purposes set forth. I

5. An electrode for a reversible galvanic battery employing an alkalineelectrolyte, said electrode containing finely-divided metallic iron oran oxid thereof mixed with copper, as and for the purposes set forth.

6. An electrode for a reversible galvanic batteryemploying an alkalineelectrolyte,

said electrode containing finely-divided me: tallic iron oran oxidthereof mixed with copflake-like conducting material, as and for thepurposes set forth.

7. An electrode for a reversible galvanic battery employing an alkalineelectrolyte, said electrode containing finely-divided metallic ironor anoxid per and flake graphite, as and for the purposes set forth.

8. An electrode for'a reversible galvanic battery employing an alkalineelectrolyte, said electrode containing an easily-reducible metal andfinely-divided electrolytically-aotive iron or an oxidthereof, theproportion of the active material being sufficiently in excess of theeasily-reducible metal to prevent oxidation of the latter on discharge,as and for the purposes set forth.

9. An electrode for a reversible galvanic battery employing an alkalineelectrolyte, said electrode containing an easily-reducible metal,finely-divided electrolytically-active iron oran oxid thereof, theproportion of the active material being sufficiently in exposessetforth.

thereof mixed with cop-' cess of the easily-reducible metal to preventoxidation of the latter on discharge, and an inert flake-like conductingmaterial, as and for the purposes set forth. 10. An electrode for abattery employing an alkaline electrolyte,

said electrode containing an easily-reducible metal, finely-dividedelectrolytically-active iron or an oxid thereof, the proportion of theactive material being sufficiently in excess of the easily-reduciblemetal to prevent oxidation of the latter on discharge, and flakegraphite admixed with the active material, 80.

as and for the purposes set forth. 1 I

"11. An electrode-for a reversible galvanic battery employing analkaline electrolyte, said electrode containing copper and finelydividedelectrolytically-active iron or an oxid thereof, the active materialbeing sufficiently in excess of the copperfto prevent oxidation of thelatter on discharge, poses set forth.

12.. An electrode for a reversible galvanic o battery employing analkaline-electrolyte, said electrode containing copper, finely-dividedelectrolytically-active iron or an oxid thereof, the active materialbeing sufficiently in excess of the copper to prevent oxidation 5 of thelatter on discharge, and an inert flakelike conducting material, as andfor the pur- 13. An electrode for a reversible galvanic batteryemploying an alkaline electrolyte, ICC

said electrode containing copper, fi-nely-di videdelectrolytically-active iron or an oxid thereof, the activematerial'being sufliciently in excess of the copper to prevent oxidationof the latter-on discharge, as and for the purposes set forth.

14. In a reversible galvanic battery employing an alkaline electrolyte,the combination with an electrode containing oxid of nickel as theoxygen storing or depolarizing 11o element, of a'second electrodecontaining electrolytically-active iron mixed with an easily-- reduciblemetal, as and for the purposes set forth.

15. In a reversible ploying an alkaline electrolyte, the combinationwith an electrode containing oxid of nickel as the oxygen storing ordepolarizing element, of a second electrode containingelectrolytically-active iron mixed with an-easily- 12o reducible metaland an inert flake-like conducting material, as and for the purposes setforth.

16. In a reversible galvanic battery employing an alkaline electrolyte,the combination withan electrode containing oxid of' nickel as theoxygen storing or depolarizing I element, of a second electrodecontaining electrolytically-active iron mixed with'an easilyreduciblemetal and flake graphite, as and for the purposes set forth.

17. In a reversible galvanic battery employing an alkaline electrolyte,the com-bination with an electrode containing oxid of reversiblegalvanic I asand for the purand flake graphite,v r05 galvanic batteryem- 15 metal on discharge, as and &

nickel as the oxygen storing or depolarizing element,'ofa secondelectrode containingelectrolytically-active iron mixed with copper, asandfor the purposes set forth.

18. In a reversible galvanic battery employing an' alkaline electrolyte,an electrode containing as its active material anelectrolytically-active insoluble metal, and a more easily reduciblemetal addedthereto, as and for the purposes set forth.

19. In a reversible galvanic battery employing an alkaline electrolyte,an electrode containing as its active material an electrolytically-active insoluble metal, and a more easily reducible metaladded thereto, the active material being in excess of the latter toprevent oxidation of the easilyreducible for the purposes set forth.

" 20. In a reversible galvanic battery employing an alkalineelectrolyte, an electrode containing as its active material anelectrolytically-active insoluble metal, a more easily' reducible metaladded thereto, and an inert flake-like conducting material added to themass, as andfor the purposes set forth.

2!. In a reversible galvanic battery employing an alkaline electrolyte,an electrode containing as its active material anelectrolytically-active insoluble metal, a more easily reducible metaladded'thereto, the active material being in excess of the latter toprevent oxidation of the easily-reducible metal on discharge, and-aninert flake-like conducting material added to the inass, as and for the4 purposes set forth.

22. In a reversible tion with an electrode containing an insolubledepolarizingactive material, of a second electrode containing aninsoluble active material which reduces with relative diliiculty mixedwith an easilyreducible metal, the proportion of the reducible activematerial being in excess of the easily-reducible metal and being also inexcess ofthe capacity of the depolarizing materiahwhereby the latter ondischarge will be prevented from oxidizing the readilyreduciblematerial, as and forthe purposes set forth.

23. In a reversible galvanic battery employing an alkaline electrolyte,the combination with an electrode containing hydrated oxid of nickel asthe depolarizing material, of a second electrode containing a mixture ofelectrolytically-active--iron and copper, the proportion of ironemployed being in excess of the copper and being also in excess of thecapacity of the nickel, whereby oxidation of the copper on discharge isprevented, as and for the purposes set forth.

'lhis specification signed and witnessed this- 29th day of September,1902. TlIOS. A; EDISON.

Witnesses:

FRANK L. DYER, J. F. RANDOLPH.

galvanic battery elnploying an alkaline electrolyte, the combina-

